In a race marred by a fatal injury to Sue Smith-trained Midnight Shadow, a stable for whom Quinlan has ridden many winners, the jockey would have been unaware that he was in trouble after jumping a fence going out down the side of the course on to the second circuit.
Up front and in first-time blinkers, the 10-year-old Windsor Avenue jumped well and, despite being headed by Storm Control after the first fence in the home straight, Quinlan didn't panic.
The front two drew clear at this point, with none of the held up horses coming close to getting into contention, but even the most optimistic Windsor Avenue supporter must have doubted he'd be ahead at the post when he was five lengths down at the last.
However, the Kerry Lee-trained Storm Control either idled or more likely emptied after the last and it would have been agonising for young Daire McConville seeing Windsor Avenue and Quinlan rally to go past him entering the final half furlong and win going away.
It was a second successive win in the race for the jockey, who was on board Takingrisks for Nicky Richards last year, also at 40-1.
Earlier, the Paddy Power Gold Cup winner and best horse in Smith's North Yorkshire stable, Midnight Shadow made a mistake at the first fence down the back straight and was quickly dismounted by Ryan Mania.
"He worked great in the blinkers in the week and I said to Sean, 'just make sure you get him out' - I didn't want him around horses," said Ellison.
"His jumping was very slick and Sean said he almost ran away with him for two miles.
"He's class, I've always said it. When we got headed I thought we'd still run well as he'd run with the choke out. I probably should have run him in the Cotswold (Chase, at Cheltenham)!
"We've put him in the National, he couldn't run with the choke out in that mind, so we'll just have to see."
On the change in fortune recently Ellison said: "Over Christmas they were scoping badly, they were working well but not running well.
"They have turned a corner now, Cormier has always been a good horse so it was nice to see him win (at Cheltenham)."
For Quinlan, securing a double on the day having landed the Grade Two Mares' Hurdle on Lucy Wadham's Miss Heritage, it was a huge thrill.
"Brian said he'd put the blinkers on the other morning and they'd lit him up," said Quinlan.
"The plan was to get a good start and get him on the front end and the blinkers made him jump today.
"I was trying to fill him up down the back and turning in I thought I'd win easy, but then Kerry Lee's horse came to me when my lad had a blow and he got away.
"When we got our second wind he's winged the last and gone away and won well. The further he went the more impressive he was."
He added: "I've been lucky in this race, it's been a great race for me. The way this lad jumped today you wouldn't be afraid of the National, before he never used to attack his fences."
